Heat transfer liq. for solar energy collector - contains liq. poly-di:methyl-siloxane! and phenyl-naphthylamine to give good heat ageing

Abstract

Abstract Heat transfer liquid compsn., for transferring heat energy from one part of another of a solar energy collector system, consists, by wt., of (A) 98-99.99 (99.5-99.9)% liquid polydimethyl-siloxane having viscosity 5-75 (10-50) cst at 25 degrees C and (B) 0.01-2 (0.1-0.5)% of a phenyl-naphthylamine. Pref. (A) contains 5 mol.% Si atom substits. other than Me, e.g. Ph, Et, 3,3,3-trifluoropropyl and/or vinyl. (B) is esp. Ph-alpha-naphthylamine. Addn. of (B) improves heat-ageing properties. In an example, the viscosity of a compsn., contg. 99.7% (A) having viscosity 50 cst and 0.3% Ph-alpha-naphthylamine, fell to 48.2 cst after 2 years in a drying oven at 200 degrees C, whereas control, consisting of 100% (A) gelled after 2 months.

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